1. Field of the Invention
The invention relates to processes for making electronic color imaging devices, particularly to a solid-state photosensitive device that has a planar array of charge-handling semiconductive photosensors in micro-registration with a multicolor planar array of filter elements. The color imaging devices are particularly useful, for example, as solid-state video cameras.
2. Description of the Prior Art
Color photosensitive devices using charge-handling solid-state image sensors of various types, for example, charge-coupling devices, known as CCDs, and charge-coupling imagers known as CCIs, have been used in video cameras. Tompsett et al., Electronics, vol. 46, pp. 162-169 (Jan. 18, 1973). To avoid optical complexity and problems with image registration, it is highly desirable that color image sensing occur at a single imaging site, e.g., at a single planar photosensitive array.
As recognized in U.S. Pat. No. 4,081,277 and divisional U.S. Pat. No. 4,168,448, both to Brault et al., it is desirable for each element in the filter array to be as close as possible to the surface of the underlying photosensor element or elements in the array. This result is accomplished in Brault et al. by producing a relatively thin, single layer multicolor filter array superimposed on the surface of the image sensor. A single layer multicolor filter array substantially reduces the possibility that light rays which pass through a filter element at an angle to the optical axis will strike a photosensor element beneath an adjacent filter element. In the preferred embodiment of Brault et al, each color filter element is rectangular in shape and has dimensions of 30 by 40 micrometers.
Brault et al. disclose a photoresist method for making a color imaging device using a transparent, polyester dye-receiving layer for receiving heat-transferable dyes. The heat-transferable dye is diffused into the polyester layer at an elevated temperature through window areas in a photoresist layer.
U.S. Pat. No. 3,284,208 to Edwin H. Land discloses a process for preparing photographic multicolor screen elements exhibiting a high degree of optical acuity and particularly adapted for use in additive multicolor photographic processes, both conventional and diffusion transfer types, by successively coating on the smooth or flat surface of a lenticular film a plurality of photoresponsive layers. Each photoresponsive layer is subjected to exposure radiation incident on the lenticular film at angles adapted to provide exposed areas of the coating contiguous each lenticule. The unexposed areas of the coating are then removed and the exposed areas dyed to provide a series of chromatic filter elements. The incident radiation employed to effect exposure of successive photoresponsive layers is directed so as to provide formation of each series of chromatic filter element in substantial side-by-side or screen relationship on the smooth surface of the lenticular film.
The technical article by Edwin H. Land entitled "An Introduction to Polavision" published in Photographic Science and Engineering, vol. 21, pages 225-236 (1977), and U.S. Pat. No. 3,734,737 to John R. Sharp describe and illustrate how the process of the above Land patent can be used to produce microscopically fine, regular multicolor stripes with great precision by the following steps: (1) embossing a film base to form fine lenticules; (2) exposing a light-sensitive layer of dichromated gelatin on the opposite side of the base through the lenticules to form line images; (3) washing away the unexposed gelatin; and, (4) dying the lines that remain. The process is repeated to complete an ultrafine array of alternating color stripes in the pattern red, green, blue, red, green, blue, and so forth. After the lenticules have been used to form lines, they are removed.